Line Segments and Rays

Geometry · Axiom Academy

Parts of a line with specific properties — where they start, where they stop, and how we name them. Start with a full line through two points A and B : arrows on both ends say it never stops. Keep only the part between the two points and you have a segment . Keep one endpoint and let the other end run off forever and you have a ray . 2. Naming Them: Why Order Matters for Rays A segment is the same set of points no matter which endpoint you name first, so . A ray is different: its name puts the endpoint first , and the second letter only says which way it points. Move the endpoint from A to B and the ray flips direction — so . and are the same finite piece — naming it backwards changes nothing. In the first letter A is the endpoint; the ray runs from A through B and onward. starts at B and points the opposite way, so it is a different ray. Both rays lie along the same line and share the points between A and B — only the direction differs. Segments: order doesn't matter Take one point and send two rays out of it in opposite directions. Together they cover the whole line — every point on one side, the shared endpoint, and every point on the other side. Two such rays are called opposite rays . You've seen how a segment, a ray, and a line are each just a part of a line — distinguished by their endpoints and how far they reach. Scroll up to replay any animation.

This is the written version of the interactive lesson above. See the full Geometry course.